It is often necessary or desirable for a person to exercise a particular muscle or group of muscles. For example, when a muscle is damaged, such as through injury or surgery, it is important to exercise the muscle to prevent atrophy and to strengthen the muscle for normal use. Further, people exercise healthy muscles to increase strength and to maintain an active and healthy lifestyle, as well as to improve their appearance. Various routines have been developed to exercise different muscle groups by forcing the muscles to contract and extend under a load, such as by moving a free weight against the force of gravity or by moving a handle whose movement is resisted by an exercise machine.
One such exercise is known as a row or a rear deltoid pull. An exerciser lies prone on a bench, or bends at the waist, and grasps a barbell below him. The exerciser then pulls the barbell to his chest and lowers it down. This exercise can be dangerous as the exerciser may drop the barbell. Further, the exerciser should have a partner to spot him in case he fails to lift the weight. Even if done properly with a partner, this exercise may not permit the user a full range of exercise since the barbell may hit the user's chest before the back muscles have contracted fully. When using free weights, the resistance provided by gravity is constant while the strength of the muscles varies over the range of motion. Consequently, the muscles are not fully loaded at each point over the range. During a row or rear deltoid pull, the hands seek to follow a curved path outward as the weight is retracted to the chest. This path cannot be followed when using a barbell because the hands are maintained at a fixed distance. This difficulty can be overcome by performing the exercise with dumbbells.
To overcome these difficulties, machines have been developed that simulate the exercise movements of a row or rear deltoid pull. In one apparatus marketed by the assignee of the instant application, a user exercises by pulling handles toward his chest. A seat and chest pad are mounted to a frame to position a user. Arms are rotatably mounted to the frame. The handles are mounted to the arms. The pivot for the arms is disposed above the seat. A cable operably connects the arms to a weight stack such that when a user pulls back on the handles, thereby rotating the arms, the weight stack is lifted and provides resistance to the exercise. The cable may be journaled over a variable radius cam to alter the distance the weight is displaced for a given amount of handle rotation at a particular point in the range of motion. Consequently, the resistance to the movement of the handles can be varied to match the strength curve of the back muscles. While this apparatus has solved many problems associated with performing rows or rear deltoid pulls with barbells and dumbbells, it did not permit the user to vary the distance between his hands while performing the exercise.
In another apparatus, disclosed in U.S. Pat. No. 5,135,456, a rowing machine is disclosed in which levers are rotatably mounted to a frame. Handles are mounted to the levers. Resistance to handle movement exercise is provided by weight plates mounted to the levers. The hinges for the levers are disposed at an angle of 17 degrees with respect to a central vertical midplane, such that the user must move his hands in defined arcs in diverging planes as he pulls back on the handles. This apparatus forces the user's hands to be spread apart at a preset rate as they are drawn back toward the chest, regardless of the user's anatomy. This apparatus does not permit the user to select his own path of hand motion for the row exercise. Rather, the motion is dictated by the angle of the hinges.
A shoulder exercise apparatus is disclosed in U.S. Pat. No. 4,603,856. In this device, a bench is provided for the user to exercise in a prone or supine position. A shaft extends from a ball and socket joint mounted to the side of the bench, and a handle is slidably mounted to the shaft. Frictional resistance is provided both at the ball and socket joint and at the sliding connection between the handle and the shaft. The user exercises by moving the handle against one or both of these resistances. While providing multiple paths of motion through the range of the ball and socket joint, this machine provides for exercising only one arm at a time, cannot coordinate the motion of two arms, and has the disadvantages associated with frictional resistance such as changing resistance due to heat buildup, and wear. Further, this machine only provides concentric action (i.e., where the muscles contract against a load). No eccentric action (i.e., where muscles extend under a load) is possible with this machine.